1. Field of the Invention
The present invention relates to a force-moment measuring apparatus for measuring forces and moments applied to a structure. In particular, the present invention relates to a parallel type six-axes force-moment measuring apparatus for correctly measuring the magnitude and direction of forces and moments applied to a structure.
2. Description of Related Art
In a conventional parallel mechanism, an end-effector and a base form a closed-loop with two or more parallel links restricting their relative movement. Any load applied to the end-effector is dispersed through the links, thus enabling stable support for large forces.
FIGS. 1 and 1A show a conventional six-axes force-moment measuring apparatus having three sensors 12 and three overload protecting rods 13 alternately and radially provided every 60 degrees around a central hub 11. A cylindrical protecting member 14 is connected to the radially distal ends of the sensors 12 and the overload protecting rods 13. Reference numeral 12s indicates a plurality of strain gauges provided on each sensor 12.
One disadvantage of conventional six-axes force-moment measuring apparatuses is that it is very difficult to machine the mechanical structure. Consequently, noise and non-linear output are caused by mutual interference due to errors machining the sensors 12. Another disadvantage is that when a unidirectional force-moment is applied, conventional apparatuses generate output in other directions. Also, it is impossible to repair a partially damaged conventional apparatus even when only a few parts of the apparatus are damaged. Using conventional apparatuses it is hard to measure large capacities and high loads, and conventional apparatuses for measuring large capacities are too large.
It is an object of the present invention to provide a parallel type six-axes force-moment measuring apparatus that is easily manufactured and repaired, and in which there is no mutual interference, and which can measure large capacities as well as high loads.
These objects are achieved by providing a parallel type six-axes force-moment measuring apparatus comprising a mechanical structure, a plurality of sensors installed at predetermined positions on the mechanical structure for measuring tensile and compressive forces applied along respective axes, the plurality of sensors outputting a sensor signal; a first signal processor for amplifying the sensor signal, the first signal processor outputting an amplified signal; a second signal processor for converting the amplified signal, the second signal processor outputting a converted signal; a signal analyzer for receiving the converted signal and calculating force and moment forces applied to the mechanical structure; and an output device for indicating the force and moment forces calculated by the signal analyzer.
According to the present invention, each sensor for a respective axis is separately machined, thus it is possible to replace individual sensors. Also, the parallel type structure according to the present invention divides loads sufficiently to measure large capacities.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.